چكيده به لاتين
Carbon dioxide in the atmosphere is one of the main causes of corrosion in reinforced concrete structures. Reinforcements buried in concrete are protected by two physical agents (concrete cover) and a chemical agent (protective oxide layer near the reinforcement surface). When carbon dioxide gas passes through the concrete cover and reaches the cross-section of the reinforcement, the PH around this layer decreases from 13 to 9 and the protective oxide layer near the reinforcement surface disappears. The corrosion process changes the mechanical properties of steel and concrete and disrupts the natural performance of the structure and has negative effects on the structure. Therefore, understanding how the reinforced concrete structures behave under the influence of corrosion is one of the important and basic issues and needs to be studied and tested. In this research, the effects of corrosion due to carbonation are first investigated and the corrosion onset time is modeled using common theories. Hasleton's 12-story frame is then modeled in opensees software, and incremental dynamic and pushover analysis is performed for the structural evaluation process. In the next step, the effects of carbonation corrosion are applied to the structure and structural analysis is performed for 30 years after corrosion for 10-year periods in different corrosion scenarios. Finally, the results of pushover and incremental dynamics analysis for each corrosion condition are reviewed and compared. The results show that due to corrosion, the values of the final moement are reduced due to corrosion, so that in the first and second scenarios, under 4 surface corrosions of the first floor columns, the final moment values for the middle column are reduced by 52 and 59%, respectively. Also, the results of nonlinear structural analysis show that corrosion reduces the capacity of the structure and changes in the functional level of the structure, so that for the first and second scenarios, the results of nonlinear static analysis show the coefficient of overstrength and ductility of the structure reduced significantly for the second scenario 16 and 56 percent, respectively. Also, coefficient of the ductility was more affected by the corrosion, so that for the second scenario the ductility coefficient decreased by 60% and for the third scenario by 24%. Therefore, corrosion in 4 surface due to the severe reduction of mechanical properties of steel and concrete is critical, so some solution such as surface protection were considered to prevent this from happening to increase the onset time of corrosion and to reduce the capacity of the structure.
